Materials used in semiconductor devices must have good semiconducting properties, good electron mobility, and the ability to host an epitaxial insulating material. Several materials are available which have good semiconducting properties and good electron mobilities but which are unsuitable because a good epitaxial insulator cannot be formed on them. Silicon, however, is widely used in semiconductor devices because epitaxial silicon dioxide forms naturally on silicon and silicon dioxide is an insulator. The disadvantage of silicon is that its mobility is not as high as in other semiconductors and silicon dioxide is not the strongest insulator available. This means that compromises in speed and performance are made when silicon is used in electronic devices.
Gallium arsenide (GaAs) is also a semiconductor and is used in some electronic applications. A device made out of GaAs would be faster than the same device made out of silicon because GaAs has an electron mobility that is considerably higher than that of silicon. Unfortunately, there is no native insulating oxide suitable for GaAs electronic devices.
Several materials have been used to provide insulating films on III-V compound semiconductor devices. Some of these films were previously used on silicon semiconductor devices. Examples include SiO.sub.2, Si.sub.3 N.sub.4, Al.sub.2 O.sub.3, and P.sub.2 O.sub.3 films. New films have also been developed specifically for the III-V compound semiconductors. For instance, A. J. Shuskus (U.S. Pat. No. 4,546,372) developed an essentially oxygen-free, amorphous osphorous-nitrogen glass passivating film for III-V compound semiconductors. Similarly, J. Nishizawa et al. (U.S. Pat. No. 4,436,770) disclose new gallium oxynitride and aluminum oxynitride insulating films for III-V compound semiconductors. These materials have found only limited application.
It would be useful to provide a new insulating material in gallium arsenide circuit elements which would provide advantages such as greater insulation and a high-break down voltage.